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NAME

rpc - library routines for remote procedure calls

SYNOPSIS AND DESCRIPTION

These routines allow C programs to make procedure
calls on other machines across the network.
First, the client calls a procedure to send a data packet to the server.
Upon receipt of the packet, the server calls a dispatch routine
to perform the requested service, and then sends back a reply.
Finally, the procedure call returns to the client.

See the header files for the declarations of the
AUTH,
CLIENT,
SVCXPRT,
and
XDR
types.

void auth_destroy(AUTH *auth);

A macro that destroys the authentication information associated with
auth.
Destruction usually involves deallocation of private data structures.
The use of
auth
is undefined after calling
auth_destroy().

AUTH *authnone_create(void);

Create and return an RPC
authentication handle that passes nonusable authentication
information with each remote procedure call.
This is the default authentication used by RPC.

Create and return an RPC authentication handle that contains
authentication information.
The parameter
host
is the name of the machine on which the information was created;
uid
is the user's user ID;
gid
is the user's current group ID;
len
and
aup_gids
refer to a counted array of groups to which the user belongs.
It is easy to impersonate a user.

Call the remote procedure associated with
prognum,
versnum,
and
procnum
on the machine,
host.
The parameter
in
is the address of the procedure's argument(s), and
out
is the address of where to place the result(s);
inproc
is used to encode the procedure's parameters, and
outproc
is used to decode the procedure's results.
This routine returns zero if it succeeds, or the value of
enum clnt_stat
cast to an integer if it fails.
The routine
clnt_perrno()
is handy for translating failure statuses into messages.

Warning: calling remote procedures with this routine
uses UDP/IP as a transport; see
clntudp_create()
for restrictions.
You do not have control of timeouts or authentication using this routine.

Like
callrpc(),
except the call message is broadcast to all locally
connected broadcast nets.
Each time it receives a response, this routine calls
eachresult(),
whose form is:

eachresult(char *out, struct sockaddr_in *addr);

where
out
is the same as
out
passed to
clnt_broadcast(),
except that the remote procedure's output is decoded there;
addr
points to the address of the machine that sent the results.
If
eachresult()
returns zero,
clnt_broadcast()
waits for more replies; otherwise it returns with appropriate status.

Warning: broadcast sockets are limited in size to the
maximum transfer unit of the data link.
For ethernet, this value is 1500 bytes.

A macro that calls the remote procedure
procnum
associated with the client handle,
clnt,
which is obtained with an RPC client creation routine such as
clnt_create().
The parameter
in
is the address of the procedure's argument(s), and
out
is the address of where to place the result(s);
inproc
is used to encode the procedure's parameters, and
outproc
is used to decode the procedure's results;
tout
is the time allowed for results to come back.

clnt_destroy(CLIENT *clnt);

A macro that destroys the client's RPC handle.
Destruction usually involves deallocation
of private data structures, including
clnt
itself.
Use of
clnt
is undefined after calling
clnt_destroy().
If the RPC library opened the associated socket, it will close it also.
Otherwise, the socket remains open.

Generic client creation routine.
host
identifies the name of the remote host where the server is located.
proto
indicates which kind of transport protocol to use.
The currently supported values for this field are "udp"
and "tcp".
Default timeouts are set, but can be modified using
clnt_control().

Warning: Using UDP has its shortcomings.
Since UDP-based RPC messages can only hold up to 8 Kbytes of encoded data,
this transport cannot be used for procedures that take
large arguments or return huge results.

bool_t clnt_control(CLIENT *cl, int req, char *info);

A macro used to change or retrieve various information
about a client object.
req
indicates the type of operation, and
info
is a pointer to the information.
For both UDP and TCP, the supported values of
req
and their argument types and what they do are:

CLSET_TIMEOUTstruct timeval // set total timeout
CLGET_TIMEOUTstruct timeval // get total timeout

Note: if you set the timeout using
clnt_control(),
the timeout parameter passed to
clnt_call()
will be ignored in all future calls.

The retry timeout is the time that "UDP RPC"
waits for the server to reply before
retransmitting the request.

clnt_freeres(CLIENT * clnt, xdrproc_t outproc, char *out);

A macro that frees any data allocated by the RPC/XDR
system when it decoded the results of an RPC call.
The parameter
out
is the address of the results, and
outproc
is the XDR routine describing the results.
This routine returns one if the results were successfully freed,
and zero otherwise.

void clnt_geterr(CLIENT *clnt, struct rpc_err *errp);

A macro that copies the error structure out of the client
handle to the structure at address
errp.

void clnt_pcreateerror(char *s);

Print a message to standard error indicating why a client RPC
handle could not be created.
The message is prepended with string
s
and a colon.
Used when a
clnt_create(),
clntraw_create(),
clnttcp_create(),
or
clntudp_create()
call fails.

void clnt_perrno(enum clnt_stat stat);

Print a message to standard error corresponding
to the condition indicated by
stat.
Used after
callrpc().

clnt_perror(CLIENT *clnt, char *s);

Print a message to standard error indicating why an RPC call failed;
clnt
is the handle used to do the call.
The message is prepended with string
s
and a colon.
Used after
clnt_call().

char *clnt_spcreateerror(char *s);

Like
clnt_pcreateerror(),
except that it returns a string instead of printing to the standard error.

Bugs: returns pointer to static data that is overwritten on each call.

char *clnt_sperrno(enum clnt_stat stat);

Take the same arguments as
clnt_perrno(),
but instead of sending a message to the standard error indicating why an RPC
call failed, return a pointer to a string which contains the message.
The string ends with a NEWLINE.

clnt_sperrno()
is used instead of
clnt_perrno()
if the program does not have a standard error (as a program
running as a server quite likely does not), or if the programmer
does not want the message to be output with
printf(3),
or if a message format different than that supported by
clnt_perrno()
is to be used.
Note: unlike
clnt_sperror()
and
clnt_spcreaterror(),
clnt_sperrno()
returns pointer to static data, but the
result will not get overwritten on each call.

char *clnt_sperror(CLIENT *rpch, char *s);

Like
clnt_perror(),
except that (like
clnt_sperrno())
it returns a string instead of printing to standard error.

Bugs: returns pointer to static data that is overwritten on each call.

CLIENT *clntraw_create(unsigned long prognum, unsigned long versnum);

This routine creates a toy RPC client for the remote program
prognum,
version
versnum.
The transport used to pass messages to the service is
actually a buffer within the process's address space, so the
corresponding RPC server should live in the same address space; see
svcraw_create().
This allows simulation of RPC and acquisition of RPC
overheads, such as round trip times, without any kernel interference.
This routine returns NULL if it fails.

This routine creates an RPC client for the remote program
prognum,
version
versnum;
the client uses TCP/IP as a transport.
The remote program is located at Internet address
*addr.
If
addr->sin_port
is zero, then it is set to the actual port that the remote
program is listening on (the remote
portmap
service is consulted for this information).
The parameter
sockp
is a socket; if it is
RPC_ANYSOCK,
then this routine opens a new one and sets
sockp.
Since TCP-based RPC uses buffered I/O,
the user may specify the size of the send and receive buffers
with the parameters
sendsz
and
recvsz;
values of zero choose suitable defaults.
This routine returns NULL if it fails.

This routine creates an RPC client for the remote program
prognum,
version
versnum;
the client uses use UDP/IP as a transport.
The remote program is located at Internet address
addr.
If
addr->sin_port
is zero, then it is set to actual port that the remote
program is listening on (the remote
portmap
service is consulted for this information).
The parameter
sockp
is a socket; if it is
RPC_ANYSOCK,
then this routine opens a new one and sets
sockp.
The UDP transport resends the call message in intervals of
wait
time until a response is received or until the call times out.
The total time for the call to time out is specified by
clnt_call().

Warning: since UDP-based RPC messages can only hold up to 8 Kbytes
of encoded data, this transport cannot be used for procedures
that take large arguments or return huge results.

This routine creates an RPC client for the remote program
prognum,
on
versnum;
the client uses use UDP/IP as a transport.
The remote program is located at Internet address
addr.
If
addr->sin_port
is zero, then it is set to actual port that the remote
program is listening on (the remote
portmap
service is consulted for this information).
The parameter
sockp
is a socket; if it is
RPC_ANYSOCK,
then this routine opens a new one and sets
sockp.
The UDP transport resends the call message in intervals of
wait
time until a response is received or until the call times out.
The total time for the call to time out is specified by
clnt_call().

This allows the user to specify the maximum packet
size for sending and receiving UDP-based RPC messages.

void get_myaddress(struct sockaddr_in *addr);

Stuff the machine's IP address into
*addr,
without consulting the library routines that deal with
/etc/hosts.
The port number is always set to
htons(PMAPPORT).

struct pmaplist *pmap_getmaps(struct sockaddr_in *addr);

A user interface to the
portmap
service, which returns a list of the current RPC
program-to-port mappings on the host located at IP address
*addr.
This routine can return NULL.
The command
rpcinfo -p
uses this routine.

A user interface to the
portmap
service, which returns the port number
on which waits a service that supports program number
prognum,
version
versnum,
and speaks the transport protocol associated with
protocol.
The value of
protocol
is most likely
IPPROTO_UDP
or
IPPROTO_TCP.
A return value of zero means that the mapping does not exist
or that the RPC system failed to contact the remote
portmap
service.
In the latter case, the global variable
rpc_createerr
contains the RPC status.

A user interface to the
portmap
service, which instructs
portmap
on the host at IP address
*addr
to make an RPC call on your behalf to a procedure on that host.
The parameter
*portp
will be modified to the program's port number if the procedure succeeds.
The definitions of other parameters are discussed
in
callrpc()
and
clnt_call().
This procedure should be used for a "ping" and nothing else.
See also
clnt_broadcast().

A user interface to the
portmap
service, which establishes a mapping between the triple
[prognum,versnum,protocol]
and
port
on the machine's
portmap
service.
The value of
protocol
is most likely
IPPROTO_UDP
or
IPPROTO_TCP.
This routine returns one if it succeeds, zero otherwise.
Automatically done by
svc_register().

bool_t pmap_unset(unsigned long prognum, unsigned long versnum);

A user interface to the
portmap
service, which destroys all mapping between the triple
[prognum,versnum,*]
and
ports
on the machine's
portmap
service.
This routine returns one if it succeeds, zero otherwise.

Register procedure
procname
with the RPC service package.
If a request arrives for program
prognum,
version
versnum,
and procedure
procnum,
procname
is called with a pointer to its parameter(s);
progname
should return a pointer to its static result(s);
inproc
is used to decode the parameters while
outproc
is used to encode the results.
This routine returns zero if the registration succeeded, -1 otherwise.

Warning: remote procedures registered in this form
are accessed using the UDP/IP transport; see
svcudp_create()
for restrictions.

struct rpc_createerr rpc_createerr;

A global variable whose value is set by any RPC client creation routine
that does not succeed.
Use the routine
clnt_pcreateerror()
to print the reason why.

void svc_destroy(SVCXPRT *xprt);

A macro that destroys the RPC service transport handle,
xprt.
Destruction usually involves deallocation
of private data structures, including
xprt
itself.
Use of
xprt
is undefined after calling this routine.

fd_set svc_fdset;

A global variable reflecting the RPC service side's
read file descriptor bit mask; it is suitable as a parameter to the
select(2)
system call.
This is only of interest if a service implementor does not call
svc_run(),
but rather does his own asynchronous event processing.
This variable is read-only (do not pass its address to
select(2)!),
yet it may change after calls to
svc_getreqset()
or any creation routines.

int svc_fds;

Similar to
svc_fdset,
but limited to 32 descriptors.
This interface is obsoleted by
svc_fdset.

svc_freeargs(SVCXPRT *xprt, xdrproc_t inproc, char *in);

A macro that frees any data allocated by the RPC/XDR
system when it decoded the arguments to a service procedure using
svc_getargs().
This routine returns 1 if the results were successfully freed,
and zero otherwise.

svc_getargs(SVCXPRT *xprt, xdrproc_t inproc, char *in);

A macro that decodes the arguments of an RPC request
associated with the RPC service transport handle,
xprt.
The parameter
in
is the address where the arguments will be placed;
inproc
is the XDR routine used to decode the arguments.
This routine returns one if decoding succeeds, and zero otherwise.

struct sockaddr_in *svc_getcaller(SVCXPRT *xprt);

The approved way of getting the network address of the caller
of a procedure associated with the RPC service transport handle,
xprt.

void svc_getreqset(fd_set *rdfds);

This routine is only of interest if a service implementor does not call
svc_run(),
but instead implements custom asynchronous event processing.
It is called when the
select(2)
system call has determined that an RPC request has arrived on some
RPC socket(s);
rdfds
is the resultant read file descriptor bit mask.
The routine returns when all sockets associated with the value of
rdfds
have been serviced.

void svc_getreq(int rdfds);

Similar to
svc_getreqset(),
but limited to 32 descriptors.
This interface is obsoleted by
svc_getreqset().

Associates
prognum
and
versnum
with the service dispatch procedure,
dispatch.
If
protocol
is zero, the service is not registered with the
portmap
service.
If
protocol
is nonzero, then a mapping of the triple
[prognum,versnum,protocol]
to
xprt->xp_port
is established with the local
portmap
service (generally
protocol
is zero,
IPPROTO_UDP
or
IPPROTO_TCP).
The procedure
dispatch
has the following form:

dispatch(struct svc_req *request, SVCXPRT *xprt);

The
svc_register()
routine returns one if it succeeds, and zero otherwise.

void svc_run(void);

This routine never returns.
It waits for RPC requests to arrive, and calls the appropriate service
procedure using
svc_getreq()
when one arrives.
This procedure is usually waiting for a
select(2)
system call to return.

bool_t svc_sendreply(SVCXPRT *xprt, xdrproc_t outproc, char *out);

Called by an RPC service's dispatch routine to send the results of a
remote procedure call.
The parameter
xprt
is the request's associated transport handle;
outproc
is the XDR routine which is used to encode the results; and
out
is the address of the results.
This routine returns one if it succeeds, zero otherwise.

void svc_unregister(unsigned long prognum, unsigned long versnum);

Remove all mapping of the double
[prognum,versnum]
to dispatch routines, and of the triple
[prognum,versnum,*]
to port number.

void svcerr_auth(SVCXPRT *xprt, enum auth_stat why);

Called by a service dispatch routine that refuses to perform
a remote procedure call due to an authentication error.

void svcerr_decode(SVCXPRT *xprt);

Called by a service dispatch routine that cannot successfully
decode its parameters.
See also
svc_getargs().

void svcerr_noproc(SVCXPRT *xprt);

Called by a service dispatch routine that does not implement
the procedure number that the caller requests.

void svcerr_noprog(SVCXPRT *xprt);

Called when the desired program is not registered with the RPC package.
Service implementors usually do not need this routine.

void svcerr_progvers(SVCXPRT *xprt);

Called when the desired version of a program is not registered
with the RPC package.
Service implementors usually do not need this routine.

void svcerr_systemerr(SVCXPRT *xprt);

Called by a service dispatch routine when it detects a system
error not covered by any particular protocol.
For example, if a service can no longer allocate storage,
it may call this routine.

void svcerr_weakauth(SVCXPRT *xprt);

Called by a service dispatch routine that refuses to perform
a remote procedure call due to insufficient authentication parameters.
The routine calls
svcerr_auth(xprt, AUTH_TOOWEAK).

Create a service on top of any open descriptor.
Typically, this descriptor is a connected socket for a stream protocol such
as TCP.
sendsize
and
recvsize
indicate sizes for the send and receive buffers.
If they are zero, a reasonable default is chosen.

SVCXPRT *svcraw_create(void);

This routine creates a toy RPC
service transport, to which it returns a pointer.
The transport is really a buffer within the process's address space,
so the corresponding RPC client should live in the same address space; see
clntraw_create().
This routine allows simulation of RPC and acquisition of RPC
overheads (such as round trip times), without any kernel interference.
This routine returns NULL if it fails.

This routine creates a TCP/IP-based RPC
service transport, to which it returns a pointer.
The transport is associated with the socket
sock,
which may be
RPC_ANYSOCK,
in which case a new socket is created.
If the socket is not bound to a local TCP
port, then this routine binds it to an arbitrary port.
Upon completion,
xprt->xp_sock
is the transport's socket descriptor, and
xprt->xp_port
is the transport's port number.
This routine returns NULL if it fails.
Since TCP-based RPC uses buffered I/O,
users may specify the size of buffers; values of zero
choose suitable defaults.

This routine creates a UDP/IP-based RPC
service transport, to which it returns a pointer.
The transport is associated with the socket
sock,
which may be
RPC_ANYSOCK,
in which case a new socket is created.
If the socket is not bound to a local UDP
port, then this routine binds it to an arbitrary port.
Upon completion,
xprt->xp_sock
is the transport's socket descriptor, and
xprt->xp_port
is the transport's port number.
This routine returns NULL if it fails.

This allows the user to specify the maximum packet size for sending and
receiving UDP-based RPC messages.

SVCXPRT *svcudp_create(int sock);

This call is equivalent to
svcudp_bufcreate(sock,SZ,SZ)
for some default size SZ.

bool_t xdr_accepted_reply(XDR *xdrs, struct accepted_reply *ar);

Used for encoding RPC reply messages.
This routine is useful for users who wish to generate
RPC-style messages without using the RPC package.

bool_t xdr_authunix_parms(XDR *xdrs, struct authunix_parms *aupp);

Used for describing Unix credentials.
This routine is useful for users
who wish to generate these credentials without using the RPC
authentication package.

void xdr_callhdr(XDR *xdrs, struct rpc_msg *chdr);

Used for describing RPC call header messages.
This routine is useful for users who wish to generate
RPC-style messages without using the RPC package.

bool_t xdr_callmsg(XDR *xdrs, struct rpc_msg *cmsg);

Used for describing RPC call messages.
This routine is useful for users who wish to generate RPC-style
messages without using the RPC package.

bool_t xdr_opaque_auth(XDR *xdrs, struct opaque_auth *ap);

Used for describing RPC authentication information messages.
This routine is useful for users who wish to generate
RPC-style messages without using the RPC package.

bool_t xdr_pmap(XDR *xdrs, struct pmap *regs);

Used for describing parameters to various
portmap
procedures, externally.
This routine is useful for users who wish to generate
these parameters without using the
pmap
interface.

bool_t xdr_pmaplist(XDR *xdrs, struct pmaplist **rp);

Used for describing a list of port mappings, externally.
This routine is useful for users who wish to generate
these parameters without using the
pmap
interface.

bool_t xdr_rejected_reply(XDR *xdrs, struct rejected_reply *rr);

Used for describing RPC reply messages.
This routine is useful for users who wish to generate
RPC-style messages without using the RPC package.

bool_t xdr_replymsg(XDR *xdrs, struct rpc_msg *rmsg);

Used for describing RPC reply messages.
This routine is useful for users who wish to generate
RPC style messages without using the RPC package.

void xprt_register(SVCXPRT *xprt);

After RPC service transport handles are created,
they should register themselves with the RPC service package.
This routine modifies the global variable
svc_fds.
Service implementors usually do not need this routine.

void xprt_unregister(SVCXPRT *xprt);

Before an RPC service transport handle is destroyed,
it should unregister itself with the RPC service package.
This routine modifies the global variable
svc_fds.
Service implementors usually do not need this routine.